1. Technical Field
The invention relates to a method and device for transmitting information to a digital video broadcasting (DVB) network.
2. Discussion of Related Art
In the branch of TV technology, it is considered a fact that analogue TV transmissions will be to an increasing extent replaced by digital TV transmissions. This development is due to the remarkable advantages offered by digital TV transmissions compared to analogue transmission. These advantages include, for instance, better image and sound quality and more efficient use of the frequency band, which enables sending more TV channels than in analogue transmission, using the same bandwidth.
The first digital TV transmission equipment have already been in use for a few years. The European digital TV system is called Digital Video Broadcasting, defined by EBU (European Broadcasting Union) and ETSI (European Telecommunications Standards Institute). Very similar systems are being used in other parts of the world. In this application, all these digital TV systems are referred to by the term DVB. In these systems, one operator typically has a data transfer capacity of 30-40 Mbit/s at his disposal, and one TV channel typically takes 3-4 Mbit/s of this capacity. Thus one operator has about ten TV channels on the average. The fixed and variable costs of the operator are such that the costs per one TV channel still remain relatively high.
FIG. 1 is a schematic outline of the operation of prior art DVB equipment. The DVB operator 19 has made a contract with three information producers or transmitters 11a, 11b and 11c on certain information to be transmitted to the end users, which information can be, for instance, films, news or other information that can be sent to the DVB network 15. The producers or transmitters 11a, 11b and 11c send the information to the operator 19 typically by a separate medium, such as a video disc or an analogue tape.
When the operator 19 has received the information to be transmitted, he draws up a transmission schedule 13, in which he arranges the information received from different suppliers 11a; 11b; 11c in a suitable manner to the data transfer capacity at his disposal. When the operator 19 has arranged the information to be sent to the network 15, it inputs the information to the DVB server 14, in which the information is coded into an information stream in the form of a standard DVB transmission coding, such as MPEG2/S (Transport Stream). After this, the information stream is sent to the DVB network 15, from which the end user""s terminal 18 receives the transmitted information stream, decodes its information content and presents it to the end user.
The problem of the prior art is, in addition to the high cost pressure on each channel mentioned above, the fact that when coding methods that consume a lot of data transfer capacity are used, the situation is often such that data transfer capacity is not used efficiently. According to FIG. 2, as much as 1-2 Mbit/s unused data transfer capacity may remain between the channels 21a, 21b, 21c and 21d. The data transfer capacity 22 that remains unused may be too narrow for sending the information stream contained in the new channel, and so part of the potential data transfer capacity of the operator remains unused.
According to a first aspect of the present invention, a method for transmitting information to a DVB network as an information stream from an information producer or transmitter to an operator of the DVB network for transmission to the DVB network, is characterized in that the producer or transmitter of the information sends the information to a well-known multicast internet address as internet protocol packets, and the operator receives the multicast internet protocol packets which contain the information from the internet.
The first aspect of the present invention, in which at least part of the transmission data of the information is transmitted from the producer of the information to the DVB operator, may be further characterized in that the information producer sends the transmission data of the information to be transmitted as packets according to the SAP/SDP protocol to a well-known multicast address in the internet, the DVB operator estimates the transmission data according to the SAP/SDP packet, and if he so desires, adds information according to the SAP/SDP packet to the IP/EPG database of the DVB/SAP server. The at least part of the information of the IP/EPG database may be coded into packets according to the SAP/SDP protocol, which may be further coded into packets according to the IP protocol and added to the information stream to be sent to the DVB network. The information of the received multicast IP packets contained in the information to be transmitted may be compared to the information to be transmitted may be compared to the information of the IP/EPG database.
According to a second aspect of the present invention, a device for transmitting information to a DVB network, which device has means for receiving the information to be transmitted, means for receiving the information to be transmitted, means for adding the received information to the information stream to be transmitted to the DVB network and means for transmitting the information stream to the DVB network, is characterized in that the device has means for receiving packets according to the multicast internet protocol. Such a device may have means for receiving SAP/SDP packets. It may further include means by which the SAP information transmitted by SAP/SDP packets coming from accepted source is updated to the IP/EPG database.
The method and device according to the invention can eliminate the problems of the prior art that were described above. It offers a cheaper solution for transmitting information to end users via the digital TV network, and at the same time enables sending more different information with the same data transfer capacity compared to the prior art. The lowering of the costs per channel improves the possibilities of small information producers to get data transfer capacity from the DVB network.
Furthermore, the invention has the advantage to the information producer that the information to be sent to the DVB network can be transmitted to the operator in real time by simple means, whereby the information producer can transmit real-time information to the DVB network, such as weather or traffic information at relatively low cost.
In addition to increased supply of information, the invention offers the operator the advantage of more efficient utilization of the data transfer capacity available, when the data transfer capacity that would otherwise remain unused can be taken into use.
The invention also has the advantage that one producer can send the same information simultaneously to a number of DVB operators, whereby the transmission costs per one operator can be reduced.
In addition, the method and device according to the invention make it possible for a DVB network user to select and receive multicast information in DVB networks that do not include a return channel.
The above advantages are achieved by increasing the number of channels available by using, instead of MPEG2 or a similar video coding method which is expensive but produces a very good image quality, a coding method, such as H.263+, which produces a slightly weaker image quality but requires less data transfer capacity. By using coding methods that require less data transfer capacity, information can be transmitted from the information producer to the DVB operator by using standardised protocols that comply with the Internet Protocol (IP) (e.g. multicast IP, UDP/RTP), which enables transmitting the information via Internet.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawing.